This invention relates to methods for producing curved elastomeric tubular articles such as hose.
A customary method for manufacturing curved hose, suitable as radiator coolant hose, for instance, involves the steps of preparing a length of uncured, flexible hose consisting of an inner tube, an outer cover, and a reinforcement positioned therebetween, and then loading the green preform onto a curved rigid metal mandrel. The hose length is then cured in an open steam autoclave while mounted on the mandrel, and then removed from the mandrel as a finished product. While this rigid mandrel process has proved largely satisfactory, serpentine configurations having extremely acute bends, which may be in three dimensions, are virtually impossible to build on rigid curved mandrels. Not only is it difficult to load and unload the hose element with these prior methods, but also problems with respect to hot tear and creasing at the inside surface of the bends arise which eventually lead to premature failure of the hose in operation.
The use of granular material such as sand is known as a flexible mandrel material in the production of curved tubular articles, such as disclosed in U.S. Pat. No. 1,877,628 to Replogle. However, the use of sand as a mandrel core in the preparation of curved hose is not satisfactory inasmuch as it produces a rough, stippled or porous interior surface upon curing; sand particles lodge within such pores and are virtually impossible to totally remove by flushing after cure. The occurrence of even residual amounts of sand in the hose may foul the water pump in the cooling system of an automobile. Other relevant art includes U.S. Pat. No. 2,974,079 to Korotkevich which discloses the use of a solid volatile or vaporizable mandrel used for splicing or joining the butted ends of hollow members of extruded rubber or plastic such as elastomeric aircraft seals.
It is a primary object of this invention to provide a method for producing serpentine configurations from elastomeric tubular material which may include extremely acute bends, using a flexible mandrel material which is totally removable from the element upon curing.